Impact of pasture contamination by copper,chromium, and arsenic timber preservative on soil microbial properties and nematodes |
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| Authors: | R D Bardgett T W Speir D J Ross G W Yeates H A Kettles |
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| Institution: | (1) Institute of Grassland and Environmental Research, Plas Gogerddan, SY23 3EB Aberystwyth, Dyfed, UK;(2) Landcare Research New Zealand Ltd, Private Bag 31902, Lower Hutt, New Zealand;(3) Present address: Institute of Environmental Health and Forensic Sciences, P.O. Box 30-547, Lower Hutt, New Zealand |
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| Abstract: | Microbial properties and nematode abundance were measured along a gradient of increasing Cu, Cr, and As concentrations (50–1300 mg Cr kg-1) in the top 5 cm of a pasture soil contaminated by runoff of preserving liquor from an adjacent timber-treatment plant. Microbial biomass C and N were significantly (P<0.05) lower in contaminated than uncontaminated soils. The amount of microbial biomass C as a percentage of total organic C declined significantly (r
2 value with Cr 0.726*) with increasing contamination, and the ratio of respired C to biomass C was significantly (P<0.05) higher with contamination. Substrate-induced respiration, microbial biomass P, and denitrification declined (r2 value with Cr 0.601, 0.833*, and 0.709*, respectively) with increasing contamination. Increasing contamination had no effect on prokaryote substrate-induced respiration but eukaryote: eukaryote substrate-induced respiration declined significantly (r
2 value with Cr 0.722*). Accordingly, the ratio of prokaryote substrate-induced respiration increased significantly (r
2 value with Cr 0.799*) with contamination. There was a significant (r
2 value with Cr 0.872*) hyperbolic relationship between sulphatase activity and contamination, with activity declining by approximately 80% at >1000 mg Cr kg-1. Increasing contamination had no effect on basal respiration, dimethyl sulphoxide reduction, and phosphatase, urease, and invertase activities. Numbers of plant-associated nematodes declined significantly (r
2 value with Cr 0.780*) with contamination. On a percentage basis, plant-feeding nematodes predominated in less contaminated soils, whereas bacterial-feeding and predatory nematodes predominated in heavily contaminated soils. The use of the fumigation—incubation procedure for measurement of microbial biomass C in heavy-metal contaminated soils is discussed. |
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| Keywords: | Heavy metals Microbial biomass Respiration Enzymes Denitrification Dimethyl sulphoxide reduction Nematodes |
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